This invention relates to a fluorine-containing polyamide-acid derivative and a polyimide produced therefrom excellent in moisture resistance and heat resistance and suitable for use as protective films for semiconductor devices, alpha particle barrier coatings for LSI (Large Scale Integration) and the like, interlayer insulators for multilevel interconnection in LSI and thin layer magnetic heads, aligning layers for liquid crystal display devices, flexible printed circuit boards, and the like.
It is well known that polyimide series polymers are useful as surface stabilizing films on exposed terminals of p,n-junctions, interlayer insulators for multilevel interconnection, alpha particle barriers for preventing soft errors of memory elements caused by natural radiation, and the like. But conventional polyimides have problems in that moisture absorption is large, adhesive properties are lowered due to moisture absorption, and the like. These problems appear practically as disconnection of wires due to corrosion of Al or Cu wiring materials in LSI, etc., blisters in insulating films at the time of rapid heating during soldering or bonding step, an increase in leakage current at p,n-junctions, and the like.
It is also found that low moisture absorption can be obtained when alkyl groups and dimethylsiloxane moieties are introduced into the polyimide skeleton, but there arises other problems such as remarkable lowering in heat resistance and solvent resistance.
As fluorine-containing polyimides, U.S. Pat. No. 4,203,922 discloses as their starting material ##STR2## J. Polym. Sci., A-1, vol 10, 1789-1807 (1972) (by J. P. Critchley at al.) discloses a polyimide having repeating units of the formula: ##STR3## U.S. Pat. No. 3,959,350 discloses a polyimide having repeating units of the formula: ##STR4## It is also known that similar polyimides have a repeating unit of the formula: ##STR5##